<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <link rel="stylesheet" href="./css/index.css" />
</head>
<body>
  <!-- 指令修饰符
   通过“.”指名一些指令后缀，不同后缀封装了不同的处理操作->简化代码
   1.按键修饰符   @keyup.enter ->键盘回车监听
   2.v-model修饰符   v-model.trim ->去掉首尾空格    v-model.number ->转数字
   3.事件修饰符   @事件名.stop ->阻止冒泡     @事件名.prevent->组织默认行为 -->

   <!-- 主体区域 -->
<section id="app">
  <!-- 输入框 -->
  <header class="header">
    <h1>小黑记事本</h1>
    <input @keyup.enter="add" v-model="todoName" placeholder="请输入任务" class="new-todo" />
    <button @click="add" class="add">添加任务</button>
  </header>
  <!-- 列表区域 -->
  <section class="main">
    <ul class="todo-list">
      <li class="todo" v-for="(item, index) in list" :key="item.id">
        <div class="view">
          <span class="index">{{index + 1}}</span> <label>{{item.name}}</label>
          <button @click="del(item.id)" class="destroy"></button>
        </div>
      </li>
    </ul>
  </section>
  <!-- 统计和清空 -> 如果没有任务了，底部隐藏掉 ->v-show实现 -->
  <footer class="footer" v-show="list.length > 0">
    <!-- 统计 -->
    <span class="todo-count">合 计:<strong> {{list.length}} </strong></span>
    <!-- 清空 -->
    <button @click="clear" class="clear-completed">
      清空任务
    </button>
  </footer>
</section>

  <script src="https://cdn.jsdelivr.net/npm/vue@2.7.16/dist/vue.js"></script>

  <script>
    //添加功能
    //1.通过v-model绑定输入框->实时获取表单元素的内容
    //2.点击按钮，进行新增，往数组最前面加unshift
    const app = new Vue({
      el: '#app',
      data: {
        todoName:'',
        list: [
          {id: 1, name: '跑步一公里'},
          {id: 2, name: '跳绳200次'},
          {id: 3, name: '游泳100米'},
        ]
      },
      methods: {
        del (id) {
          //console.log(id) => filter 保留所有不等于该id的项
          this.list = this.list.filter(item => item.id !== id)
        },
        add() {
          if (this.todoName.trim() === '') {
            alert('请输入任务名称')
            return
          }
          this.list.unshift({
            id: +new Date(),
            name: this.todoName
          })
          this.todoName = ''
        },
        clear () {
          this.list = []
        }
      }
    })
  
  </script>
</body>
</html>